July 1991
Volume 32, Issue 8
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Articles  |   July 1991
Species differences in the effects of endothelin-1 on myo-inositol trisphosphate accumulation, cyclic AMP formation and contraction of isolated iris sphincter of rabbit and other species.
Author Affiliations
  • A A Abdel-Latif
    Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
  • Y W Zhang
    Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
Investigative Ophthalmology & Visual Science July 1991, Vol.32, 2432-2438. doi:
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      A A Abdel-Latif, Y W Zhang; Species differences in the effects of endothelin-1 on myo-inositol trisphosphate accumulation, cyclic AMP formation and contraction of isolated iris sphincter of rabbit and other species.. Invest. Ophthalmol. Vis. Sci. 1991;32(8):2432-2438.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The authors investigated the effects of endothelin-1 (ET1) on inositol trisphosphate (IP3) production, 1, 2-diacylglycerol (DAG) formation, measured as phosphatidic acid (PA), cAMP formation, and contraction in iris sphincter of different mammalian species. They found that ET1 is a potent agonist for IP3 production, DAG formation, and contraction in rabbit, dog, cat, and pig iris sphincters, and for cAMP formation in all species that were investigated--rabbit, dog, cat, pig, bovine, monkey, and human sphincters. In the bovine model, ET1 induced cAMP formation in a dose-dependent manner, with an EC50 of 28 nM. This is the first report that showed an effect of the peptide on the adenylate cyclase system. In rabbit sphincter, ET1 induced a significant increase in IP3 production by 30 sec and reached a 6-fold level more than control within 1 and 5 min. ET1-stimulated IP3 production is dose dependent with an EC50 of 45 nM, this value is about 100- and 56-fold lower than those we reported for substance P and carbachol, respectively. ET1 also increased 32P labeling of PA more than 6-fold; and in rabbit sphincter, ET1 is a more potent agonist in contracting the sphincter than in contracting the dilator (the EC50 values for sphincter and dilator were 46 and 120 nM, respectively). L-type Ca2+ channels are not involved in IP3- and contraction responses because several blockers of these channels did not affect the ET1-induced responses, implying that in the iris sphincter, ET1 elicits the physiologic response through the G protein activation of phospholipase C and/or adenylate cyclase and not through the activation of voltage-dependent Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

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